Atomic structures of a Si (111) surface are dynamically observed at a 2 s/frame velocity over a scanning field about 150 Å×150 Å using a fast scanning tunneling microscope (FSTM). A FSTM has been developed and it features a compensation method for probe tip servo position error in the constant current mode. The compensation value is derived from the ratio of tunnel current fluctuation and tunnel current (Δ I/I) in differential-type tunnel current equation. The FSTM provides first dynamic observation of a residual gas molecule adsorption on atomic defects in 7×7 Si adatom reconstructions using a video tape recorder. In addition, a thermal drift of about 10 Å /s, about 30 min after direct electric flash heating of the sample for Si surface cleaning, can be easily observed.
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